Solid state effects in the electronic structure of ladder-type poly(p-phenylene)s and oligo(p-phenylene)s

In this paper, the spin-dependent photophysical properties of poly(para-phenylene)-type ladder-polymers (LPPP), a highly luminescent polymer with emission yields of ∼30% in film and ∼100% in solution, and of five- and seven-member ladder-type oligo(para-phenylenes) (LOPP5 and LOPP7, respectively) are determined via their photoluminescence (PL) emission, PL excitation, and PL-detected magnetic resonance (PLDMR) spectra. In the latter experiment, we investigated spin-sensitive properties, such as the formation of polaron pairs as a function of conjugation length and interchain interaction. The observation of a PLDMR quenching resonance upon increasing the temperature and/or the excitation wavelength is discussed in relation with the formation of polarons and polaron pairs from delocalized and localized states, respectively.